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Adding subset result detection to node.js example #73

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Mar 19, 2023
Merged

Adding subset result detection to node.js example #73

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45 changes: 29 additions & 16 deletions examples/hb-subset.example.node.js
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Original file line number Diff line number Diff line change
@@ -1,13 +1,14 @@
// Based on https://github.com/harfbuzz/harfbuzzjs/issues/9#issuecomment-507874962
// Which was based on https://github.com/harfbuzz/harfbuzzjs/issues/9#issuecomment-507622485
const fs = require('fs');
const readFileAsync = require('util').promisify(fs.readFile);
const writeFileAsync = require('util').promisify(fs.writeFile);
const { readFile, writeFile } = require('fs').promises;

const SUBSET_TEXT = 'abc';

(async () => {
const { instance: { exports } } = await WebAssembly.instantiate(await readFileAsync(__dirname + '/../hb-subset.wasm'));
const fontBlob = await readFileAsync(__dirname + '/Roboto-Black.ttf');
const { instance: { exports } } = await WebAssembly.instantiate(await readFile(__dirname + '/../hb-subset.wasm'));
const fontBlob = await readFile(__dirname + '/Roboto-Black.ttf');

const t = performance.now();
const heapu8 = new Uint8Array(exports.memory.buffer);
const fontBuffer = exports.malloc(fontBlob.byteLength);
heapu8.set(new Uint8Array(fontBlob), fontBuffer);
Expand All @@ -20,9 +21,9 @@ const writeFileAsync = require('util').promisify(fs.writeFile);
/* Add your glyph indices here and subset */
const input = exports.hb_subset_input_create_or_fail();
const unicode_set = exports.hb_subset_input_unicode_set(input);
exports.hb_set_add(unicode_set, 'a'.charCodeAt(0));
exports.hb_set_add(unicode_set, 'b'.charCodeAt(0));
exports.hb_set_add(unicode_set, 'c'.charCodeAt(0));
for (const text of SUBSET_TEXT) {
exports.hb_set_add(unicode_set, text.charCodeAt(0));
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Though it is safe for this example (the text is all ASCII), charCodeAt gives UTF-16 code units (including surrogate pairs), you should use codePointAt instead.

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Thanks for the correction, let me fix it.

}

// exports.hb_subset_input_set_drop_hints(input, true);
const subset = exports.hb_subset_or_fail(face, input);
Expand All @@ -31,16 +32,28 @@ const writeFileAsync = require('util').promisify(fs.writeFile);
exports.hb_subset_input_destroy(input);

/* Get result blob */
const result = exports.hb_face_reference_blob(subset);

const data = exports.hb_blob_get_data(result, 0);
const subsetFontBlob = heapu8.subarray(data, data + exports.hb_blob_get_length(result));

await writeFileAsync(__dirname + '/Roboto-Black.subset.ttf', subsetFontBlob);
console.log(`Wrote subset to: ${__dirname}/Roboto-Black.subset.ttf`);
const resultBlob = exports.hb_face_reference_blob(subset);

const offset = exports.hb_blob_get_data(resultBlob, 0);
const subsetByteLength = exports.hb_blob_get_length(resultBlob);
if (subsetByteLength === 0) {
exports.hb_blob_destroy(resultBlob);
exports.hb_face_destroy(subset);
exports.hb_face_destroy(face);
exports.free(fontBuffer);
throw new Error(
'Failed to create subset font, maybe the input file is corrupted?'
);
}

// Output font data(Uint8Array)
const subsetFontBlob = heapu8.subarray(offset, offset + exports.hb_blob_get_length(resultBlob));
console.info('✨ Subset done in', performance.now() - t, 'ms');
await writeFile(__dirname + '/Roboto-Black.subset.ttf', subsetFontBlob);
console.info(`Wrote subset to: ${__dirname}/Roboto-Black.subset.ttf`);

/* Clean up */
exports.hb_blob_destroy(result);
exports.hb_blob_destroy(resultBlob);
exports.hb_face_destroy(subset);
exports.hb_face_destroy(face);
exports.free(fontBuffer);
Expand Down